MAGNET WITH UNIFORM MAGNETIC FIELD

摘要

PURPOSE: To reduce a magnetic field error based on hysteresis by making a polar plate element oriented toward bases of magnetic pole pieces which is made of a material having a relative permeability a specific value or more smaller than a relative permeability of a material of a polar plate element oriented toward a utility volume. CONSTITUTION: The uniform magnetic field magnet has polar plate units 12 and 13 which are disposed as spaced by narrow correction gaps 14 and 15 from bases of magnetic pole pieces 10 and 11 oriented toward a yoke plate 3. The magnet also has at least two polar plate elements 12a and 12b which are made of different materials and are disposed parallel to each other. The polar plate elements 12a and 12b are spaced from each other by a gap 22 having a predetermined width W. In the respective magnet pole pieces 10 and 11, the polar plate element 12a oriented toward the bases 10b and 11b is made of the material having a relative permeabilityμγ1 that is smaller at least by a coefficient 5 than a relative permeabilityμγ2 of at least 10000 of the material of the polar plate element 12b oriented toward a utility volume N. Thereby a magnetic field error based on hysteresis can be reduced.